Objective:To evaluate the effect of day surgery on length of stay and average costs in a triple-A hospital in northern Jiangsu Province, and to provide the basis for further promoting the implementation of day surgery. Methods: The day surgery group included 732 patients who undergone day surgery in 2015. The control group included 753 patients who did not undergone day surgery in the same period in 2014. Frequency statistics method and t-test were performed to analyze the data. Results: Average costs were found to be significantly decreased in the day surgery group. Conclusion: Day surgery plays an effective role in reducing the burden on patients and improve the efficiency of the use of medical resources.